divisibility rules

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  • March 11, 2013 at 1:15 pm
    Paula Spicer
    Participant

    I have a 4th grader (perfectionist). Right this moment she is learning divisibility rules. Is this necessary and do you teach it? It is a lot to remember, memorizing mostly. I don’t remember doing these, and I think it would be easier for her just to go ahead and divide the number out herself to see if there is a remainder. This is causing a meltdown in the house right now, and I guess I’m wanting someone to tell me it’s ok to skip this part 🙂 Anyone else have trouble with this, what did you do?

    March 11, 2013 at 1:49 pm
    Tristan
    Participant

    We’ve done this with my oldest and I have to say they’ve been SO SUPER HELPFUL when she works with larger numbers and fractions (needing to reduce) so she can quickly figure out if a number is divisible by something. Really, I would learn them! If you want some help for her to memorize them you could always print out a chart of them for a while to go over daily.

    Here is one with a story type rhyme: http://whattheteacherwants.blogspot.com/2011/01/divisibility-rules.html

    Here is a great page giving you an idea of just why it’s so useful: http://www.mathgoodies.com/lessons/vol3/divisibility.html

    Here is a printable chart: http://www.mff.org/mmc/divisibility_rules_chart.pdf

    Here is another chart with examples: http://www-mce.stjohns.k12.fl.us/teachers/rogersd/0E927120-0118C716.9/Divisibility%20Rules%20Chart.pdf

    One last PDF with a chart on page 1 and practice on page 2 with answers on page 3: http://www.edonyourown.com/math/mathworksheets/DivisibilityRulesWorksheet.pdf

    March 11, 2013 at 2:18 pm
    Sue
    Participant

    Tristan! This stuff is fabulous!!! Thanks!!!

    My oldest is studying algebra, she does not particularly like math, so whatever she learns she often tosses aside after she finishes a unit. She has been having trouble deciding whether she can simplify a fraction when the numerator or denominator is a large number, so these divisibilty rules will be a big help to her.

    Also, I see that a rule for the number 7 is only contained in one of the charts. Is that simply because it is so complicated? It does seem a little too complicated to remember very easily.

    March 11, 2013 at 2:24 pm
    Sue
    Participant

    Here’s another question: Does anyone who uses MUS know if Mr. Demme covers these divisibility rules in his lessons? At which level would he introduce them?

    March 11, 2013 at 2:26 pm
    Paula Spicer
    Participant

    Thanks Tristan, I’m printing off the poem right now and putting it in her math book. Sometimes it takes the silliest things to help understand something 🙂

    March 11, 2013 at 3:16 pm
    Tristan
    Participant

    SUE – They do cover them in MUS! Check out lesson 11 in Epsilon: Finding Common Factors and Divisibility. He covers 2, 5, 10 as obvious ones (even, end in 5 or 0, end in 0), 3’s and 9’s. He does not have kids learn rules for divisible by 4, 6, 8 but mentions in the teacher’s manual that these will be divisible by 2 more than once and that becoming familiar with multiples of these numbers helps. He does not cover 7s in this lesson as it is difficult (which is also why I think most of the printables I linked do NOT cover 7s either).

    The rules of divisibility are a help to speed up many things. I say every little bit helps!

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